Ruthenium Nucleation Layer for Low Resistivity Memory Conductors
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in efficiently forming electrically conductive layers with low resistance and high purity, particularly in the context of vertical NAND strings, where conventional methods involve complex deposition processes and high resistivity materials.
Innovation Solution
The formation of electrically conductive layers in three-dimensional memory devices involves a ruthenium portion and a conductive material portion, where ruthenium is deposited closer to the memory film than the conductive material, using atomic layer deposition and selective deposition processes to achieve lower resistivity and avoid deposition on insulator layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional deposition processes are used to form electrically conductive layers, then the process is simpler, but the resistivity is high and purity is low
Solution Approach 1:
The electrically conductive layer is segmented into two distinct portions: a ruthenium portion deposited directly on the memory film, and a conductive material portion deposited on the ruthenium portion. This segmentation allows each layer to be optimized for its specific function, with ruthenium providing low resistivity and high purity at the interface, while the conductive material provides overall conductivity.
Solution Approach 2:
Different materials are used at different locations within the electrically conductive layer structure. Ruthenium is placed at the critical interface with the memory film where low resistivity and high purity are most important, while other conductive materials are used in regions where overall conductivity is the primary requirement. This local optimization resolves the contradiction between process simplicity and layer quality.
2Reliability
If high resistivity materials are used in electrically conductive layers, then the deposition process is simpler, but the electrical performance is poor
Solution Approach 1:
The electrically conductive layer is formed as a composite structure combining ruthenium and other conductive materials. Ruthenium provides the low resistivity and high purity properties needed at the memory film interface, while the additional conductive materials contribute to overall layer conductivity and manufacturability. This composite approach achieves superior electrical performance without sacrificing ease of manufacture.
Solution Approach 2:
Ruthenium serves as an intermediary layer between the memory film and the other conductive materials. It provides a low-resistivity, high-purity interface that facilitates excellent electrical contact, while also serving as a foundation for depositing additional conductive materials. This intermediary structure resolves the contradiction by enabling both low resistivity and ease of manufacture through sequential deposition.
3Manufacturing precision
If complex etchback processes are used, then deposition coverage is improved, but the manufacturing process becomes more complex
Solution Approach 1:
Ruthenium is deposited preliminarily on the memory film surface before depositing the other conductive materials. This preliminary ruthenium layer ensures complete and precise coverage of the memory film interface, creating a foundation that eliminates the need for subsequent etchback processes to achieve proper deposition coverage. The preliminary action of ruthenium deposition resolves the contradiction between coverage precision and process complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the resistivity of the conductive layers, simplifies the integration process, and avoids the need for high resistivity materials and complex etchback processes, leading to more efficient and reliable memory device fabrication.
Implementation Method 1
forming a ruthenium portion comprising ruthenium within a respective backside recess
Implementation Method 2
forming a conductive material portion comprising a material other than ruthenium on surfaces of the ruthenium portion
Data Source
AI summary
A memory film and a semiconductor channel can be formed within each memory opening that extends through a stack including an alternating plurality of insulator layers and sacrificial material layers. After formation of backside recesses through removal of the sacrificial material layers selective to the insulator layers, a ruthenium portion can be formed in each backside recess, and a polycrystalline conductive material portion can be formed on each ruthenium portion. Each ruthenium portion can be employed in lieu of a tungsten seed layer to function as a lower resistivity seed layer that enables subsequent deposition of a polycrystalline conductive material. The resulting electrically conductive lines can have a lower resistivity than conductive lines of comparable dimensions that employ tungsten seed layers.